# Mean

What is Mean Value?

Mean is an average of the given numbers: a calculated central value of a set of numbers.

In simple words, it is the average. It’s also the meanest because it take the most math to figure it out.

When you add up all the values and divide by the number of values it called as Arithmetic Mean

To calculate, just add up all the given numbers then divide by how many numbers are given.

Example: What is the mean of 3, 5, 9, 5, 7, 2 ?

Now add up all the given numbers:

3 + 5 + 9 + 5 + 7 + 2 = 31

Now divide by how many numbers provided in the sequence:

316= 5.16

5.16 is the answer

Measures of central tendency, or averages, are used in a variety of contexts and form the basis of statistics. To calculate the arithmetic mean of a set of data we must first add up (sum) all of the data values (x) and then divide the result by the number of values (n). Since  is the symbol used to indicate that values are to be summed (see Sigma Notation) we obtain the following formula for the mean (¯x).

$\bar{x}=\frac{\sum x}{n}$

In the case of a discrete probability distribution of a random variable X, the mean is equal to the sum over every possible value weighted by the probability of that value; that is, it is computed by taking the product of each possible value x of X and its probability P(x), and then adding all these products together.

Types

Geometric Mean: The geometric mean of two numbers x and y is xy. If you have three numbers x, y, and z, their geometric mean is 3xyz.

$\large Geometric\;Mean=\sqrt[n]{x_{1}x_{2}x_{3}…..x_{n}}$

Example: Find the geometric mean of 4 and 3 ?

Geometric Mean =$\sqrt{4 \times 3} = 2 \sqrt{3} = 3.46$

Harmonic Mean: the harmonic mean is used to average ratios. For two numbers x and y, the harmonic mean is 2xy(x+y). For, three numbers x, y, and z, the harmonic mean is 3xyz(xy+xz+yz)

$\large Harmonic\;Mean (H) = \frac{n}{\frac{1}{x_{1}}+\frac{1}{x_{2}}+\frac{1}{x_{2}}+\frac{1}{x_{3}}+……\frac{1}{x_{n}}}$

Root Mean Square (Quadratic): The root mean square, is used in many engineering and statistical applications, especially when there are data points that can be negative.

$\large X_{rms}=\sqrt{\frac{x_{1}^{2}+x_{2}^{2}+x_{3}^{2}….x_{n}^{2}}{n}}$

Contraharmonic Mean: The contraharmonic mean of x and y is (x2 + y2)/(x + y). For n values,

$\large \frac{(x_{1}^{2}+x_{2}^{2}+….+x_{n}^{2})}{(x_{1}+x_{2}+…..x_{n})}$<

#### Practise This Question

Statement 1: Range of a data set gives the measure of its spread.

Statement 2: Range of a data set is given by: Highest observation + Lowest Observation.

Pick the correct option.